This invention relates to an integral heated probe for an injection molding system which has an insulation and locating hoop portion which encloses circumferential air chambers and seats in the cavity plate to accurately locate the probe.
Heated probes are well known in the injection molding industry. An early example is shown in U.S. Pat. No. 4,120,086 to Crandell entitled "Method of Making Electrically Heated Nozzle" which issued Oct. 17, 1978. Another example is shown in the applicant's U.S. Pat. No. 4,376,244 entitled "Injection Molding Heated Probe" which issued Mar. 8, 1983 which describe a heated probe mounted in a fixed position in a well in the cavity plate with the melt flowing around it to the gate. The applicants's U.S. Pat. No. 4,611,394 entitled "Method of Manufacture of an Injection Molding Integral Heated Probe" which issued Sept. 6, 1986 discloses a method of making probes with external longitudinally extending melt channels. Another probe is shown in Japanese Utility Patent Application No. 57-69184 to Yoshida filed Oct. 11, 1980. The applicant's U.S. Pat. No. 4,576,567 entitled "Injection Molding System Having an Insulation Sleeve" which issued Mar. 18, 1986 shows a further improvement wherein a thermoplastic insulating sleeve having matching channels fills the space around the nozzle. More recently, the applicant's U.S. Pat. No. 4,669,971 entitled "Valve Gated Probe" which issued June 2, 1987 shows a system in which a number of probes are fixed to a common manifold and actuated together to provide valve gating. While these previous probes are satisfactory for many applications, there are disadvantages which arise with high pressure and/or high temperature molding. As shown for instance in the applicant's U.S. Pat. No. 4,576,567 referred to above, it is well known to locate the nozzle in a well in the cavity plate by having a hollow cylindrical insulation bushing. However, where the melt bores pass beneath the insulation bushing, there is a relatively thin wall section which can burst if the injection pressure is too high. Furthermore, there is considerable heat loss through the insulation bushing to the cooled cavity plate which is not acceptable if uniform melt temperature is critical. In some cases, the insulation bushing which contacts the cavity plate is made of a titanium alloy to reduce the heat loss problem, but it still exists.